This application addresses broad Challenge Area (04) Clinical Research and specific Challenge Topic, 04-OD-101: Develop and validate behavioral metrics to measure the impact of chronic pain. Acute pain is a normal sensation triggered in the nervous system to alert a person to possible injury. Chronic pain persists over a longer period of time and often is resistant to medical treatments. Chronic pain complaints include headache, low back pain, cancer pain, arthritis pain, neurogenic pain (pain resulting from damage to the peripheral nerves or to the central nervous system itself), psychogenic pain (pain not due to past disease or injury or any visible sign of damage inside or outside the nervous system). After an acute injury or onset of pain it is natural for persons to engage in "pain behaviors"- behaviors that may communicate to others that a person is experiencing pain. They include behaviors such as resting, guarding, facial expressions, asking for help, taking medication, and other observable displays. Initially these behaviors may be helpful in protecting a person from further injury or increased pain or in eliciting support and assistance from others. A problem arises when pain behaviors persist beyond the acute phase and contribute to subsequent psychosocial and physical disability. Research indicates that interventions such as counter conditioning can ameliorate the negative impacts of persistent pain behaviors and decrease subsequent disability. To understand the role of pain behavior in initiating and modulating chronic pain, standardized and validated measures are needed. This project will develop measures of pain behavior based both on self- and observer reports. It will extend previous pain behavior measurement work by (1) applying sophisticated psychometric and statistical methods, (2) using larger scale sampling, (3) comparing various approaches to measuring pain behaviors (i.e., self-report, observer-report, and frequency counts), and (4) assessing the relationship between pain behavior and future disability. To develop pain behavior measures, we will administer candidate pain behavior items to 600 patient/observer pairs-200 each with osteoarthritis, lower back pain, and multiple sclerosis. 225 of these will be followed every 3 months for an additional 5 time points. These longitudinal data will be used to evaluate whether particular pain behaviors (e.g. guarding) are more predictive of disability over time and to identify patient subgroups with different trends in pain and disability over time. Better understanding and measurement of pain behaviors will help chronic pain researchers and clinicians address pain resistant to typical medical treatments PUBLIC HEALTH RELEVANVE: After an acute injury people may engage in "pain behaviors" (e.g. resting, guarding, facial expressions, asking for help). These behaviors can be helpful initially, but if they persist past their adaptive lifetime they can contribute to disability. The proposed project will develop standardized measures of pain behaviors to help researchers and clinicians identify persons'levels of different pain behaviors and help them test interventions that target persistent pain behaviors in hopes of decreasing later disability.